After the campaign announcement, Romney tweeted this morning, "I am proud to announce @paulryanvp as my VP. Stand with us today. #RomneyRyan2012."

"U.S. Rep. Paul Ryan is in his seventh term in Congress representing Wisconsin's First Congressional District. He is Chairman of the House Budget Committee, where he has worked tirelessly leading the effort to rein in federal spending and increase accountability to taxpayers," according to a biography released by the Romney campaign.

Sen. Rob Portman, R-Ohio, called ABC News late Friday to say he is in Columbus, Ohio, and will be doing a 100-mile bike ride on Saturday in his home state, not attending a vice presidential announcement in Norfolk, Va.

Earlier ABC News learned that at least two other possible vice presidential candidates have been called by Mitt Romney and told they have not been chosen. Romney did not tell either of them who he had picked.

ABC News saw Tim Pawlenty in downtown Manchester, N.H., and not heading to the airport. He told ABC News that he will not be in Virginia today and is not Romney's vice presidential pick. He said he knew the identity of the pick but would not reveal it.

"I didn't enter this thinking I would be the VP candidate so I'm not disappointed," Pawlenty said. "I'm excited about [Romney's] candidacy and I'm excited about having him as president."

Incidentally, Tagg Romney, Mitt Romney's son, was with both Ryan and Pawlenty on Friday, ABC News has learned.

ABC News also has learned Sen. Marco Rubio, R-Fla., is not going to be the vice presidential candidate.

The location of the event in Virginia had raised the possibility that the pick could be Virginia Gov. Bob McDonnell, another name that has surfaced as Romney's vice presidential selection process has proceeded. McDonnell has been slated to appear at campaign events today alongside Romney.

Late Friday, McDonnell would not tell ABC News whether he was Romney's pick.

"I guess we'll have to stay tuned and see tomorrow," he said. "You know, there's only a couple people that know and that's Mitt Romney, so we'll find out tomorrow."

The news of Romney's impending announcement first broke via Twitter, when Romney's communications director, Gail Gitcho, tweeted, "@MittRomney will announce his VP pick tomorrow in Norfolk. Download the VP app to be the first to know. mi.tt/Mitt-VP."

ABC News' Arlette Saenz and Michael S. James contributed to this report.